1. Technical Field
The present invention relates to a cuvette, and more particularly, it relates to a cuvette employed for analysis of a specimen such as blood (including plasma or serum) or urine.
2. Background Information
Various shaped cuvettes are known in general. For example, Japanese Patent Laying-Open No. 8-101209 discloses a cuvette having a square cylindrical lower portion and a cylindrical upper portion and configured such that outer and inner surfaces of the lower portion each has a multangular shape in horizontal cross section, as shown in FIG. 16. Japanese Patent Laying-Open No. 2002-196007 discloses a cuvette configured such that outer and inner surfaces from an upper portion to a lower portion each has a circular shape in horizontal cross section, as shown in FIG. 17.
Japanese Utility Model Laying-Open No. 6-40848 discloses a cuvette in which a central portion is formed in a square cylindrical shape, upper and lower portions arranged so as to hold the central portion therebetween are each formed in a cylindrical shape, and each of outer and inner surfaces of the central portion is configured to have a square shape in horizontal cross section, as shown in FIG. 18.
Each of the aforementioned cuvettes is employed for analysis of a specimen including steps of dispensing, stirring, and optically measuring the specimen and a reagent by automatically transferring the same on an analyzer. For example, each of the aforementioned cuvettes is transferred by grasping the upper portion of the cuvette with a transfer apparatus having a hand member capable of grasping the upper portion of the cuvette. A sample stored in the cuvette is stirred by vibrating the cuvette through drive of a vibration motor in a state of grasping the cuvette by the transfer apparatus. In the optical measurement, the cuvette storing the sample is irradiated with a measuring beam in a state where the cuvette is received in a receiving hole.
However, the cuvette in Japanese Patent Laying-Open No. 8-101209 shown in FIG. 16 is configured such that a measuring beam is applied to a square cylindrical portion of the lower portion of the cuvette. In such a structure, even when the cuvette inserted into a receiving hole is placed at a prescribed position, if the cuvette rotates at the position, an angle at which light enters from a light source is not constant with respect to a wall surface of the square cylindrical portion. In this case, the state of refraction or reflection of light by the wall surface varies, whereby there is a possibility that reproducibility of measurement results is deteriorated. Therefore, the analyzer must be configured such that the cuvette placed in the receiving hole does not rotate. Even in a case where the analyzer must be configured such that the cuvette placed in the receiving hole does not rotate, the analyzer must be configured such that a specific wall surface of the square cylindrical portion of the cuvette is placed so as to face the light source at least when the cuvette is inserted into the receiving hole. Therefore, in the cuvette disclosed in Japanese Patent Laying-Open No. 8-101209, structures of respective components of the analyzer including a transfer apparatus is disadvantageously complicated.
The cuvette in Japanese Utility Model Laying-Open No. 6-40848 shown in FIG. 18 is configured such that a measuring beam is applied to the square cylindrical portion of the central portion of the cuvette. Thus, this cuvette has a problem similar to that of the cuvette shown in FIG. 16.
In the cuvette in Japanese Patent Laying-Open No. 2002-196007 shown in FIG. 17, the inner surface of the cuvette has a circular shape in horizontal cross section, and hence a sample in the cuvette smoothly flows keeping a state where the sample is not sufficiently immingled, without disturbing the flow, even when vibration is applied to the cuvette. Thus, when vibration is applied to the cuvette to stir a specimen or a reagent in the cuvette, if stirring time is short, stirring may be insufficient depending on a condition such as ratio or viscosity of the specimen or the reagent. Consequently, in the cuvette disclosed in Japanese Patent Laying-Open No. 2002-196007, stirring of the sample disadvantageously requires long time.